of Articulated Coralline Algae
are structurally organized into cellular filaments. Thalli and developed
stalks can be either uniaxial or multiaxial, depending on which genera one
is taking into account. Algal size and thickness are usually determined
by both genetic and environmental factors.
The articulates are often
referred to as geniculates due to their possession of flexible, uncalcified
genicula, which operate like joints. Genicula are the primary characteristic
that distinguish the articulates from crustose forms of corraline. Organization
of genicula differs between classes of corallines in the numbers of cell
tiers or layers. However, the basic structure of these tissues is consistent
throughout all articulates.
A genicula from
a Bossiella specimen.
The other primary
tissues in the articulates are referred to as intergenicula. These
calcified branch segments are extremely rigid, like bones. Most intergenicula
have cuticles that cover their calcium carbonate walls. Intergenicula play
a crucial role in the reproduction and growth of geniculates. Reproductive
conceptacles develop only on intergenicula. The growth of articulates is
dependent upon the elongation of intergenicula and division of these growing
segments via the formation of new genicula. Decalcification of the intergenicula reveals
underlying tissue just like that found on other red algae.
Calliarthron and its broad intergenicula.
Most articulates have both primary
and secondary pit connections between their cells that arise with growth-related
cell division. These connections are sealed by the formation of mucosal
pit plugs. Another type of interesting cell connection exists within the
geniculates--cell fusion. Many coralline cells are able to fuse with other
coralline cells from the same or a different plant if cells touch for a
prolonged period of time.
Evolution | Ecology | Systematics | Mechanics | Pigmentation | Morphology | Reproduction | Life
History | References | Procedures Acknowledgements | Main
Ian Ehrenreich. All rights reserved.